Antony Francis worked as a fundraiser for NCH for six years. Although he has signed a confidentiality agreement as part of his settlement with the charity, Third Sector understands that documents submitted to an employment tribunal last week claimed that as a black gay man he "did not fit the mould" and was not given responsibilities appropriate to his experience.
While Francis was limited to corporate accounts worth £20,000, he claimed that more junior female colleagues handled blue-chip donors worth £500,000 a year.
"Other NCH employees often referred to the company fundraising team as the 'Pony Club' as it was very clique-driven and mainly consisted of white, female, straight, blue-eyed blondes," he claimed.
Francis began to see bereavement counsellors at the Terrence Higgins Trust in 2001, but when his line managers found out, they wrongly assumed he was HIV positive, he claimed.
NCH declined to make an official comment, citing the charity's policy not to discuss individual current or former employees.
However, it is understood that the charity disputes the claims made by Francis, including the allegations about the 'Pony Club'.
A spokesman said: "Our fundraising team is very diverse and NCH has an excellent record on equal opportunities.
"We would never employ someone because of how they looked - the allegations are insulting to the fundraising team."